Variable pitch propeller



Feb. 27, 1940. H. omees VARIABLE PITCH PROPELLER Filed July 9, 1937 2 Sheets-Sheet 1 YINVENTOR. lv 0 n H D H995 ATTORNEY.

I. H. DRIGGS 2,192,034

I VARIABLE PITCH PROPELLER' Feb. 27 1940.

Filed July 9, 1957 2 Sheets-Sheet 2 'INVENTOR. Ivan H Drlggs ATTORNEY.

Patented Feb. 27, 1940 UNITED STATES PATENT OFFICE VARIABLE PITCH PROPELLER Ivan'H. Driggs, Towson, Md., assignor to The Glenn L. Martin Company, Baltimore, Md.

Application July 9, 1937, Serial No. 152,677

4 Claims. ('01. 17 -164) one can easily adapted for use with any of the above mentioned classes or sub-classes of variable'pitch propellers. Y

Various and sundry types and forms of vari- 20 able pitch propellers have heretofore beenproposed; but the only types ofvariable pitch propellersknown to me to have proven to any satisfactory degree of practicability are those of the power operated automatic type, such as the 2 Hamilton Standard, which employs oil pressure for turning the blades, or the Curtiss electrically operated propeller. There has not been, tomy knowledge, an automatic variable .pitch propeller of the self operated ty'pe heretofore proposed thatv 30 has proven to be practical and it is -one object of this invention to provide a propeller construction of the self operated automatic type that shall not only be theoretically sound, but prac tical in operation.

85 It is another object to provide a propeller con- I struction that shall be practical and readily adaptable for use as a manually operated variable pitch propeller or a power or self operated automatic variable pitch propeller.

40 Another object is to provide. a propeller construction of the automatic type that shall consist of a minimum number -of relative movable parts.

Afurther object is to provide in a propeller 45 of the variable pitch type novel means for adjusting the pitch of the propeller blades that shall be simple, rugged, durable, and compara-- tively inexpensive to manufacture. A'still further object is to provide in a pro- 50' peller of the variable pitch type novel means for connecting the propeller blades to a propeller hub in such 'a manner as to cause theseveral forces acting upon the blades. during operation to automatically provide the desired pitch durin: all operating conditions.

the provision of a propeller construction which- The above and other objects will be made apparent throughout the further description of-the' invention when taken in connection with the accompanying drawings, wherein like reference characters refer to like parts.- It is to be dis- 6 tinctly understood that the drawings are not a definition of the invention but merely illustrate certain forms of the invention, by means of which the invention may be efiectuated.

In the drawings: i 10 Figure 1 is a front elevational view, more'f'or less diagrammatic, of a propeller together with the associated power mechanism embodying one form of the invention.

Figure 2 is a side elevational view of the embodiment shown in Figure 1', illustrating in .broken lines a position which the propeller may assume under certain conditions.

Figure 3 is an enlarged fragmentary sectional view takenalong the line 3-3 of Figure 1 Figure 4 is a fragmentary view showing two positions of the propeller blade.

Figure 5 is a side elevational view of a propeller, illustrating another embodiment of the invention.

Figure 6 is a front elevational view similar to Figure 1, illustrating still another embodiment' of the invention.

Figure 7 is a side elevational view of the embodiment shown in Figure 6, and

Figure 8 is a fragmentary sectional view, more or less diagrammatic, showing a power means for changing the pitch of propellerblades embodying the invention, which may be either manually-or automatically operated. Referring to the drawings, Figures 1 to 4, inclusive, illustrate a preferred form of the inven-- tion, wherein the propeller is of the self operated automatic type. This embodiment consists of a power shaft l0, driven by the power plant 40 representedin its entirety by H, a novel pr0- peller hub l2 fixedly mounted on the shaft Ill and {adapted to be driven thereby, the hub l2 being adapted to accommodate a pair of blades I3. gOne form of the present discovery resides' 5 in the manner inwhich the blades I3 are hingedly connected to the hub 12 as shown at I. As is apparent from the drawings, each .of the blades. I 3 is hingedly connected to the hub I! in such a manner that the axes oftheassociated hinges ll lie in the plane of rotation of the blades 13, the axes of the hinges being disposed at an angle of less than ninety degrees with the axes or chords of the associated propeller blades. u

The operation of this construction may be illustrated thusly: the arrow IS in Figure 1 indicates the direction of rotation of the propeller blades. l6 and I1 indicate the leading and trailing edges, respectively, of the blades l3. Immediately upon applying power to the shaft ID, the air thrust acting upon the blades I3 will tend to turn them forwardly about their respective axes or hinges M as shown at l8 in Figure 2. Because of the inclination of the axes M, the trailing edges I! of each of the propeller blades will travel a greater linear distance than the leading edges I6 of the blades, thereby changing the pitch of the blades, and in the particular instance just described, the pitch of the blades is reduced. It follows that upon reducing the pitch of the blades that the load on the motor or power plant II is reduced, at which time the power plant having comparatively light load thereon readily speeds up to provide the desired propeller revolutions, during which time the centrifugal force developed by the rotation of the blades tends to move the blades backwards about their respective hinges l4 and toward and into the plane of revolution of the propeller. Inasmuch as the trailing edges of the propeller blades will travel a greater linear distance than the leading edges as above pointed out, it follows that the pitch of the propeller blades will be increased as the blades are moved rearwards under the action of the centrifugal force.

- For the purpose of this application, the term propeller thrust is defined as the action of the propeller blades upon the surrounding air to effect the movement of the propeller forwardly through the air. Now, with this explanation, there are two forces operating oppositely one to the other upon the propeller blades, which may be better stated thusly: the propeller thrust is at all times tending to decrease the pitch of the propeller blades, while the centrifugal force developed by the rotation of the propeller tends at all times to increase the pitch of .the propeller blades. With this understanding it will, of course, be understood that in the construction of propellers of different sizes and for differentduties, the weight of the blades as well as the angle at which the blades are hingedly connected to the hub must be determined to suit the specific installation concerned. 7 Figure 3 merely shows spring-held members 2| employed for limiting the turning movement of the blades l3 about the hinges l4 and likewise to effect a cushioned stop for the blades at their extreme limits of turning about the hinges l4.

Figure 4 illustrates a front elevationalview of one of the blades l3 illustrated in Figures 1 and-2. The primary purpose of this figure is to illustrate that the blade I 3, in turning about its axis l4, does not only move forwardly and rearwards relative to the plane of revolution of the propeller, but "that the blade simultaneously moves laterally with respect to the plane of revolution.

Figure 5 illustrates another embodiment of the invention, wherein the blades l3 are hinged about axes I4, the latter, while each being disposed at an angle of less than ninety degrees with the axis or- .chord of the corresponding propeller blade, each is disposed in a plane at substantially right angles'to the plane of revolution of the propeller. In this embodiment the pitch of the blades is subject also to two opposing forces; namely, centrifugal force developed by the rotation of the blades similar to that described in connection with Figures .1 and 2 in that in the specific form shown the centrifugal force tends to increase thepitch of the blades. The other force is here defined as propeller drag and that is the resistance that the air sets up to the rotation of the propeller blades. This propeller drag tends to turn the blades about the axes M in a direction opposite to the direction of rotation of the propeller. This tendency is directed toward decreasing the pitch of the blades. This feature results in the fact above stated that the trailing edges I! of the blades travel a greater linear distance than the leading edgesduring a given movement of the blades about their axes l4. Here the pitch of the propeller blades is responsive to the opposing forces, of propeller drag and centrifugal force of the blades.

Figures 6 and 7 illustrate still another embodiment of the invention, wherein the blades l3 are hingedly connected to the hub l2 in an intermediate position between the positions illustrated in Figures 2 and 5. In this form the pitch of the propeller blades is responsive to the centrifugal force developed during the rotation of the blades and the resultant forces of the propeller thrust and propeller drag acting on the blades, the resultant forces, namely the propeller thrust and propeller drag, tending to decrease the pitch of the blades, while the centrifugal force developed by the rotation of the blades tends to increase the pitch of the blades.

Figure 8 is a fragmentary sectional view through a power shaft l0, more or less diagrammatic, illustrating a hydraulic oroil pressure mechanism for moving the blades l3 about the axes Id. The root or inner ends of the blades l3 in this embodiment are of slightly different construction than those shown in the other embodiments and provide shoulders 22 on each side of the inner ends of the blades l3 for cooperating with power operated lugs 2la. These power operated lugs 2 la differ from the cushioned stops 2| illustrated in Figure 3 in that they are connected with a hydraulic system represented in its entirety by 23, whereby each of the lugs 2Ia is carried by a piston 24 positioned in a cylinder 25. These lugs 2la are simultaneously actuated in opposite directions through the conventional valve mechanism illustrated at 26, the latter may be operated either manually or automatically by any conventional means for supplying oil from a source by way of pipes 21 or 28 dependent upon the direction that the propeller blades are to be turned about their axes ll.

Accordingly, I have provided a propeller construction which may be adaptable'for use as a manually operated propeller as well as an automatic variable pitch propeller of either the power operated or self operated type.

Some of the important features of the inventhe hinged joints; the weight of the blades will be materially reduced and the factor of safety greatly increased in view of he reduction of the above mentioned bending stresses, and for the vibration in the blades caused by irregularities.

of air flow through the propeller disc caused by the presence of a wing or imsymmetrical nacelle behind it will be eliminated, since the blades can adjust themselves immediately to the local conditions of air flow.

While the several forms of the invention have been described in connection with a two bladed propeller, it is to be distinctly imderstood that the invention may be utilized in a propeller having any number of blades. It is to be further understood that the teachings of the invention may be utilized by positioning the hinge axes in some other plane or angle than those specifically illustrated here. One of the primary purposes of showing the different embodiments in this application is to teach that the invention may be employed in various forms of construction without departing from the spirit and scope of the invention. The invention is defined by the appended claims. 2

I claim:

1. A screw propeller comprising a plurality of blades and a hub having an opening therein adapted to receive a drive shift, a hinge transversely inclined with respect to the longitudinal axis of said shaft connecting each blade to said hub, oppomtely extending shoulder portions on opposite sides of each of said blades adjacent said hinge, and a hydraulic control means operatively engaging each of said portions for changing the pitch of said blades by turning each blade on its hinge.

2. A screw propeller comprising a plurality of blades each of which has opposed elements transversely extending from said blades, a hinge for each of said blades, a hub, and hydraulic means for changing the pitch of each of said blades, said hub having an opening adapted to receive a drive shaft, each hinge vhaving its longitudinal axis transversely inclined with respect to the longitudinal axis of said opening, and each hydraulic means consisting of a hydraulically operated lug cooperatively engaging each of said elements upon each of said blades to change the pitch of each blade by its rotation about its hinge.

3. A screw propeller as in claim 2, a hollow drive shaft in said opening in said hub, feed lines for supplying fluid to said hollow shaft, and individual piston means communicating with said hollow shaft and operatively connected to each of said lugs.

4. A screw propeller comprising a plurality of blades each of which has opposed lugs and a hub having an opening-therein adapted to receive a drive shaft, a hinge connecting each blade to said hub and having its axis transversely inclined with respect to the longitudinal axis of said opening, and a hydraulic control means engaging each of said opposed lugs of each blade for turning each blade on its hinge to adjust the pitch of said blade.

IVAN H. DRIGGS.- 

